The present invention generally relates to photography and more particularly, to a photographic camera capable of functioning in accordance with information received from a roll of film to be loaded in the camera.
Various information are expected to be received from a roll of film to be loaded in the camera. For example, a series of signals formed by detecting the passages of the sprocket holes of the film may be information of the amount of movement of the film which is being wound up, and code signals located on the film surface or the film catridge are also useful information to be received from the film. The camera can function in accordance with such information in various ways, i.e. the camera is capable of indicating the frame number of the film by counting the series of signals formed by detecting the passage of the sprocket holes, and the camera is capable of automatically winding-up the film to the first frame or sensing that the film has been wound-up to the last frame by counting the sprocket hole signals. Further, the code signal received by the camera can inform the camera of the number of available frame of the loaded film, or the position of the first frame or the last frame.
The prior art has proposed various camera relating to the above mentioned camera functions, such as disclosed in U.S. Pat. Nos. 3,485,157 and 4,294,527, Research Disclosure, April 1980, Number 192, page 142, and Japanese Laid Open Patent Application Nos. 54/26722 and 54/70031.
As to the detection of the passages of the sprocket holes, the prior art conventionally proposes various arrangements for detecting film sprocket holes, through detection of electrical conduction or non-conduction according to the presence or absence of the film sprocket holes by the employment of switch means and the like, for example, in photographic cameras.
The known film sprocket hole detecting arrangements as described above, however, are inevitably accompanied by the so-called chattering or generation of vibration noises at electrical contact portions thereof, and if the chattering as described above is left as it is, there are such disadvantages that, for example, in a case where the number of frames of the film which have been exposed is to be counted by the signal from the electrical contact portions, false counting of more than two sprocket holes may undesirably occur, in spite of the fact that only one sprocket hole has passed through the detecting portion. In order to overcome the disadvantages as described above, there have conventionally been proposed various arrangements in which chattering elimination circuits are provided in the detecting portions. However, the known chattering elimination circuits as described above are fundamentally arranged to remove high frequency components of signals for producing only low frequency components, and have such a drawback that the response thereof tends to be slow. More specifically, when the winding speed of the film is increased, there arises such a problem that the detection signal is not produced due to a delay in the response of the chattering elimination circuit in spite of the detection of sprocket holes. Moreover, there are cases where contact pieces for the chattering elimination circuit are subjected to bounding at a period much larger than that of the chattering even after settling of the chattering, due to adhesion of dust and dirt thereto or fatigue of the contact pieces. However, it is impossible for the chattering elimination circuit to remove such undesirable signals arising from the bounding at the contact pieces.
Furthermore, in the case where the film, for example, in the form of a roll is arranged to be wound by a motor, the roll of film may be wound up at least by one frame without stopping in the course of winding, but in the case of manual winding, the roll of film is not necessarily wound up continuously all through one frame, but may be fed intermittently or suspended in its winding-up in some cases. In the cases as described above, if starting of generation or signal output of the sprocket hole detecting signal disappears, with simultaneous interruption of the manual advancing of the film, in the course of film feeding at which the film equivalent to one frame has not completely been advanced, the output for the sprocket hole detection signal is in an unstable state at which time, a large number of sprocket hole detection signals are undesirably developed even by a slight external impact applied to the camera. The abnormal sprocket hole detection signals as described above can not be corrected by the known chattering elimination circuits, and thus, it becomes difficult to correctly effect the counting of the frames which have been exposed for photographing.
Further, with respect to the camera designed to function in response to the code signals representative of the number of the available frames, or the position of the first or last frame of the film, the prior art fails to consider how to deal with a case that a film without such code signals is loaded in the camera.